2017 Cardiovascular Research Day Abstract Book

93
Impact of miR-33 antagonism on atherosclerotic plaque size and cholesterol content in
nonhuman primates
Tong Li, MD 1 • Lei Cai, PhD 1 • Sierra Paxton 1 • Courtney Burkett 1 • Peter Hecker, MS 1 •
Ryan Temel, PhD 1
1CVRC, University of Kentucky
Graduate Student
Introduction: Elevated LDL cholesterol (LDL-C) is a major risk factor for coronary heart disease
(CHD). Statins are used to lower LDL-C and CHD risk but do not completely eliminate CHD events
caused by atherosclerotic lesion rupture. By stimulating macrophage cholesterol efflux and
promoting anti-inflammatory macrophage polarization, antagonism of microRNA-33a (miR-33a) in
mice reduces the cholesterol content and size of atherosclerotic lesions. Mouse studies have limited
translational value since mice do not develop coronary artery atherosclerosis and express only one
of the two miR-33 family members found in humans. Since nonhuman primates (NHPs) have miR-
33a and miR-33b and develop coronary artery atherosclerosis, NHPs are the best preclinical model
for determining the therapeutic potential of miR-33 antagonism. We hypothesize that NHPs treated
with miR-33 antagonist will have decreased plaque size and cholesterol content.
Methods: Male cynomolgus monkeys (n=36) were fed for 20 months a high fat/high cholesterol
diet, which caused severe hypercholesterolemia. At the end of the 20-month progression phase, a
subset of monkeys (n=12) were euthanized to collect tissues. The remaining monkeys were
switched to a cholesterol-lowering “chow” diet and treated with either vehicle (n=12) or anti-miR-
33 (n=12) for 6 months. Formalin-fixed right coronary arteries (RCA) were split into five ~3 mm
sections, paraffin embedded, and cut into 5 µm slices. Lesion area, defined as the region between
the lumen and internal elastic lamina, was measured for each RCA section and then averaged for
each animal. Cholesterol was extracted from a section of the fixed thoracic aorta and the free and
total cholesterol levels were determined by GC-FID. Esterified cholesterol (EC) = total cholesterol –
free cholesterol (FC).
Results: No significant difference among the progression, vehicle, and anti-miR-33 groups were
observed for RCA lesion area (P=0.60) and thoracic aorta FC (P=0.24). Thoracic aorta EC was
significantly increased in the progression versus the regression groups (P